This invention relates to a method for selectively capturing metal ions from a solution containing ions of heavy metals, and preferably at least two such metals.
Industrial effluents from metal mines and factories contain a variety of metal ions among which heavy metal ions are known to have an adverse influence on human and animal bodies and thus are desired to be removed completely before the effluents are actually discarded into rivers, lakes, oceans and other bodies of water. As ways for eliminating such metal ions, there have been proposed a method wherein industrial effluents are treated with a metal capturing agent such as a condensed phosphate or ethylenediaminetetraacetic acid and a method wherein industrial effluents are biologically treated with microorganisms. However, these methods are not as yet practically applicable for several disadvantageous reasons. Thus, in the first case, the metal capturing agent is too expensive for the treatment of large amounts of effluent and, in the second, a sufficient level of elimination is not achieved by the biological treatment. On the other hand, if a variety of metals contained in effluents could be recovered selectively and separately, it would be a significant advance in the art, particularly in respect to re-utilization of the recovered metals. However, there is up to now no known method for treating effluents which can serve this purpose.